1. Field of the Disclosure
The present disclosure relates to a liquid crystal display (LCD) device, and more particularly, to a method of fabricating an array substrate for an in-plane switching (IPS)-mode LCD device including a common electrode and pixel electrodes having fine line widths.
2. Discussion of the Related Art
A liquid crystal display (LCD) device, which is advantageous to displaying moving images and popularly used for televisions and monitors due to a high contrast ratio, may form images based on optical anisotropy and polarization of liquid crystals (LCs).
The LCD device may include an LC panel as an essential component. The LC panel may be formed by interposing a liquid crystal layer between two substrates disposed in parallel to each other and bonding the liquid crystal layer to the two substrates. In the LCD device, a direction in which LC molecules are arranged may be changed according to an electric field generated in the LC panel to obtain a difference in transmittance.
Recently, an active-matrix (AM)-type LCD device configured to drive LCs according to a vertically generated electric field has been widely employed because the AM-type LCD device has a high resolution and is highly capable of embodying moving images. However, the AM-type LCD device has poor viewing angle characteristics because LCs are driven due to a vertically applied electric field.
For this reason, various methods for overcoming a narrow viewing angle have been proposed. Among these, a method of driving LCs according to a horizontal electric field is being watched with interest.
FIG. 1 is a schematic cross-sectional view of a LC panel of a typical in-plane switching-mode LCD device.
Referring to FIG. 1, a lower substrate 1 serving as an array substrate and an upper substrate 3 serving as a color filter substrate may be disposed apart from and opposite each other, and a liquid crystal layer 5 may be interposed between the upper and lower substrates 1 and 3.
A common electrode 21 and a pixel electrode 25 may be formed on the same planar surface of the lower substrate 1. The liquid crystal layer 5 may operate according to a horizontal electric field L generated by the common electrode 21 and the pixel electrode 25.
As described above, the in-plane switching-mode LCD device may include the common electrode 21 and the pixel electrode 25 formed on the lower substrate 1, and generate the horizontal electric field L between the two electrodes 21 and 25 so that LC molecules can be arranged in parallel to the horizontal electric field L that is parallel to the upper and lower substrates 1 and 3. Thus, a viewing angle of the LCD device may be widened.
Meanwhile, in the in-plane switching-mode LCD device, since the liquid crystal layer 5 operates due to the horizontal electric field L formed between the pixel electrode 25 and the common electrode 21, it is impossible to drive the liquid crystal layer 5 disposed on the pixel electrode 25 and the common electrode 21. Accordingly, an aperture ratio may be reduced by as much as the areas of the pixel electrode 25 and the common electrode 21.
For this reason, to improve an aperture ratio, a pixel electrode and a common electrode having a fine line width are required for recent in-plane switching-mode LCD devices. However, formation of the pixel electrode and the common electrode with a line width of less than about 2.5 μm is technically limited due to the resolution limit of current exposure tools.